This proposal is for continuation of a broad program of research on basic visual physiology, using arthropod eyes as the principal experimental material. Specifically we are interested in the spectral properties of visual pigments as revealed by microspectrophotometry, the packaging of these pigments in the rhabdoms and ommatidia so as to provide a basis for color vision and polarized light analysis, the properties of invertebrate metarhodopsin, the regeneration of visual pigments, and their relation to receptor adaptation. A second line of approach concerns the transmission of information through the optic ganglia, and more specifically the synaptic organization of the lamina ganglionaris, the receptive fields and polarized light sensitivities of second-order cells in the external chiasma of crabs, and the functional significance of dark currents and hyperpolarizing post-synaptic potentials in the lamina ganglionaris of insects.